[Devel] [PATCH hci-8.1 v5 0/3] dm-qcow2: truncate unused tail of image on suspend

[Andrey Zhadchenko]

Reviewed-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>

On 10/10/26 14:46, Alexander Ivanov wrote:
> On postsuspend dm-qcow2 truncates the image file only down to
> file_preallocated_area_start, so clusters at the end of the file freed
> by discard are never given back and the file never shrinks.
> 
> This series makes postsuspend scan the refcount blocks backward and
> truncate the file to the end of the last used cluster. Close and
> reload to RO go through postsuspend too, so the tail is given back in
> these cases as well.
> 
> Patch 1 adds qcow2_md_page_read_sync() helper, which is needed by the
> scan. Patch 2 is a small cleanup of duplicate prefixes in QC_ERR/QC_INFO
> messages. Patch 3 does the actual truncation.
> 
> https://virtuozzo.atlassian.net/browse/VSTOR-148171
> 
> v5:
> - Add Reviewed-by line.
> 
> v4:
> - Patch 1: document in the comment that the caller must ensure no read
>    of the page is in flight.
> - Patch 3: say in the commit message that close and reload to RO go
>    through postsuspend too.
> 
> v3:
> - Split from the common series with dm-ploop: dm-ploop patches are
>    sent as a separate series.
> - Patch 1: rename qcow2_get_md_page_sync() to qcow2_md_page_read_sync(),
>    reword commit message and comment.
> - Patch 2: new patch.
> - Patch 3: start the scan from file_preallocated_area_start instead of
>    the end of the file and clamp the result to it, as the last cluster
>    may be partial; print the scan error with %pe and drop the duplicate
>    "dm-qcow2:" prefix from it.
> 
> v2:
> - Add dm-ploop support (patches 3-6), as requested in v1 review.
> - dm-qcow2: move get_md_page_sync() to a separate patch as
>    qcow2_md_page_read_sync() and use it in qcow2_parse_header() as well.
> - dm-qcow2: start the refcount scan below file_preallocated_area_start
>    instead of the end of the file, and truncate to the used end directly
>    instead of min(file_preallocated_area_start, used end).
> 
> Alexander Ivanov (3):
>    dm-qcow2: add qcow2_md_page_read_sync() helper
>    dm-qcow2: drop duplicate prefix from QC_ERR/QC_INFO messages
>    dm-qcow2: truncate unused tail of image on suspend
> 
>   drivers/md/dm-qcow2-map.c    | 56 ++++++++++++++++++++++++
>   drivers/md/dm-qcow2-target.c | 83 +++++++++++++++++++++++++++---------
>   drivers/md/dm-qcow2.h        |  3 ++
>   3 files changed, 121 insertions(+), 21 deletions(-)
>